John Carmack on Eclipse performance

[Froglegs]

   You can look at the source for Doom 3, it is written in C with
classes more than C++. But that was years ago, and Carmack has
taken an interest to functional programming so perhaps they are
more up to date nowadays.. although I'm guessing they have a ton
of legacy code written in C style and C with classes style..

   Perhaps he is using a haskell IDE for eclipse?